Rock boring and like tool



July 20, 1943- P. cox

ROCK BORING AND LIKE TOOL 2' Sheets-Sheet l Filed April 9, 1941 July 20, 1943. P. cox 2,324,679

ROCK BORING AND LIKE TOOL Filed April 9 1941 2 sheets-sheet 2 I NN" II II II II ./LL .f--1 I I I I I I I I I rf I I I I I I I I I I I I I I. I

Patented July 20, 1943 ROCK BORING AND LIKE TOOL Percy Cox, Keston Park, England; Nellie Louise Cox administratrix of Percy Cox, deceased Application April 9, 1941Serial No. 387,729 In Great Britain April 26, 1940 4 Claims. (Cl. 2555-76) This invention relates to rock boring and like tools and is particularly concerned with a tool adapted for the counterboring of previously fdrilled holes in rock and similar formations either natural or articial. In rock blasting operations the size of the explosive charge` is limited by the diameter of the shot hole which should be small, otherwise not only is the cost of drilling excessive but the eiiicacy of the charge will be reduced. The normal sizeof shot hole is from one and a half to three inches in diameter. Attempts have been made to enlarge the inner ends of the shot holes for accommodating bigger charges, but hitherto no satisfactory way of Iaccomplishing this has been evolved.

The present invention aims to provide a simple and effective means for enlarging or counterboring drilledV holes in rock formations and particularly to enable the inner ends of shot holes tok be enlarged for the purpose described above. Another object of the invention is to provide a tool for this purpose which is of simple `and rugged construction, and one which is adapted to be operated by the apparatus usually available for rock drilling.

Other and further objects and advantages attained by the invention will be pointed out or indicated hereinafter or will be apparent to one skilled in the art upon an understanding of the invention or its employment in practice.

According to the invention a counterboring tool is provided comp-rising a body which may be introduced into the hole Vand rotated therein, having cutters movably mounted in the body, which cutters are arranged to be fed laterally into counterboring position by actuating means having thrust engagement with the bottom of the hole. It will be understood that the body is rotated and fed forwardly by any suitable means, preferably by the usual jack rods employed inthe preliminary drilling operations, and the forward feed in conjunction with the aforesaid thrust means forces the cutters into engagement with the sides of the hole to form a counterbore of thedesired dimensions.

In one form of the invention, the actuating means for the cutters comprises a centre piece or rod slidably mounted in the body and having a part engaged with the vcutter adapted to effect an outward feeding movement thereof when the actuating means is moved rearwardly relatively to the body. The cutters may be provided with cam surfaces' engaged by the actuating means for effecting the lateral feed.

According to a further feature of the inven-- tion, the` cutters are pivotally mounted inthe body,` and- "preferably lie in slots which extend parallel to the axis of the tool.

In one form of the invention, each cutter is` of flat cross-section and two cutters are mounted upon a common pivot pin. Each cutter is preferably formed with a cam slot. The slidable centre piece has a fork end carryingV a cross-pin which engages the two cam slots, which are formed so that as the fork moves rearwardlythe cutters are fed outwardly into counterbomng position.

In another form of the invention, the cutters are actuated by a rack and pinion arrangement. In this form, the body has a fixed centre piece for engaging the bottom of the hole, `and the rack members are mounted on a carrier which is movable relatively to the body; the rotary drive is transmitted to the carrier and thence through the rack members by engagement with the slots in which they slide. Each cutter comprises a fiat plate-like element having` a toothed sectoral portion near its rear end for' engagement with the rack members. According to` a feature of this construction, each rack lies alongside one of the cutters` andforms a lateral guide when the cutter is extended outwardly.

According to a further feature `of the invention. the cutters have shaped side faces adapted to engage the sides of the hole when displaced out' ward1y,and carry cutting diamondsin standard means is pro-vided to receive `the lateral thrust on the .cutters in their `operative position. Such means `may comprise thrust members extending partly into the slots in which the cutters are mounted, and may be xed or movable. 'Ihus operated, the rackassociated with one of the cutters is arranged to extend alongside the other cutter and to formV a lateral abutment which is adapted to receive the side thrust on the cutter. The provision for taking up lateral thrust is important in that it permits the use of a relativelyV are not to be accorded any interpretation having the effect of restricting the claims, short of the true and most comprehensive scope of the invention in the art.

The invention may be embodied in various constructional forms, two of which will now be described by way of example and illustrated by the accompanying drawings in which:

Figure 1 is an elevation of a rock counterbo-ring tool according to the present invention;

Figure 2 is an elevation of the tool taken in a plane at right-angles to the piane of Figure 1, showing the cutters removed;

Figure 3 is a cross-section of the tool, with the cutters removed, taken on the line 3 3 of Figure 1;

Figure 4 is an end View of the forward end of the tool;

Figure 5 is an elevation of the sliding fork for actuating the cutters;

Figure v6 is a side view of one of the cutters; v"Figure 6a 'is an end View of the cutter;

Figure 7 is an elevation of another form of rock counterboring tool;

l"Figure 8 is an elevation of the body of the tool taken on a' plane at right-angles to the plane of Figure 7.

Figure 9'is an end view of the body of the tool taken from the rear;

Figure l is a cross-section taken on the line III-III of Figure 7;

Figure 1l is a cross-section taken on the line II--II of Figure V'7;

Figure l2 is an elevation of the carrier member for the toothed racks;

Figure 13 i's an end view of the carrier member;

Figure i4V is an elevation of the stop member for the carrier member;

Figures l and 16 are side and end views respectivelyof one of the cutters;

Figure I7 is an end View of a part of one of the cutters showing the method of mounting the diamonds.

In carrying the invention into effect according to one convenient mode as illustrated in Figures 1 to 6, the rock counterboring tool is provided with a body or head I of generally tubular form having attened sides and adapted to be attached at 2 to a jack rod or like actuating means such as vare generally used with rock drills for rotating the tool within the hole. Towards the rear end of the body a pair of diametrically disposed lateral slots 3 are provided for accommodating the cutters. A transverse pivot pin 4 mounted in the body towards the rear of the slots 3 receives two cutters 5 which are flat in crosssection and have shaped edges for engaging the sides of the hole. A recess 'I in the upper end of each cutter engages a xed pin 8 mounted in the body I which limits the lateral or outward swinging movement of the cutter. The width of the cutter slots 3 is slightly in excess of twice the thickness of the individual cutters 5 so that the latter may lie side by side when in their withdrawn position. A guide member 9 consisting of a rectangular plate is welded in position to occupy` half the width towards the lower end of each slot 3, and serves to take lateral thrust exerted on the cutter when the latter is in an extended position and in cutting engagement with the sides Aof the hole. rIt will be appreciated that this arrangement allows of the use of cutters of relatively large cross-section as compared with the diameter of the body of the tool, since their width may be nearly equal to the latter. In their withdrawn position the cutters lie wholly within the body of the tool as shown in dotted lines in Figure 1.

Each cutter is provided with a cam slot I0 inclined to the general length of the cutter, and this slot is adapted to be engaged by an actuating pin to swing the cutter outwardly upon its pivot Q as the actuating pin is moved rearwardly. The slot I@ is preferably slightly curved as shown and also includes a straight portion I I. A recess I2 provided on one edge of each cutter is adapted to lit over the thrust receiving member 9 when the cutter is in its completely withdrawn position.

The common actuating pin I3 which engages the oppositely inclined slots in the two cutters is carried by a fork I4 sliding within the cylindrical bore I5 of the body and is integral with a rod I6 which at its forward end is attached to a centre piece I1 having a point I8 which is adapted to be engaged with the bottom of the shot hole. This centre piece is formed with a iiat I9 on one side slidably engaged lby a pin 20 which prevents rotation. A cylindrical bore 2| within the centre piece I1 accommodates a helical spring 22, the rear end of which bears against a shoulder 23 in the body, this shoulder also forming a gui-de for the rod I6. The spring 22 tends to lmaintain the centre piece I'I in its foremost position, in which also the cutters are completely withdrawn within the slots 3.

The cutters have shaped operative cutting edges as shown in Figure 6, including a curved portion which rst engages the sides of the hole and a straight portion which is inclined to the general direction of the length of the cutter. |The edge 6 is also slightly inclined with respect to the pivotal axis of the cutter and is'drilled to accommodate standard tapered diamond mountings as indicated at 24.

The tool is attached at 2 to the usual jack rod or drilling rod and is introduced into the shot hole until the point of the centre piece is engaged with the bottom of the hole. Further forward movement of the tool will cause the cutters tobe vfed outwardly until their operative edges 6 engage the side of the hole and the tool is then rotated to cut a counterbore. By continuously exerting a forward feeding pressure on the tool the cutters will be progressiveiy displaced outwardly totheir maximum extent, which will occur when the actuating pin I3 reaches the end of the curved portion of the cam slot II). Further forward feeding movement will bring the pin I3 into the straight part II of the cam slot and movement of the pin along this slot portion will not result in any further outward displacement of the cutters. In this way a parallel-sided counterbore will be cut having a length corresponding to the length of the straight portion II of the cam slot. It will be understood that by employing centre pieces El of different lengths, the position of the counterbore relative to the bottom of the hole may be varied. It will be noted that the tool has a central bore which extends into the cutter slots and washing liquid may be supplied by this means.

In carrying the invention into effect according to another mode, as illustrated in Figures 7 to 17, the cutters are arranged to be carried at the forward end of the body of the tool and the cutter feed is effected by means of a rack and pinion arrangement. In this form the tubular body 25 has a forwardly extending centre piece 26 secured therein. This centre piece may however be re'- movable, permitting centre pieces' of `different lengths to'be used. A paii` of .diametrically op- 'posedflateral slots 2l' areprovided near. thefor'- wardV endiofthe bodyf and 'areadaptedtoaci commodate two opposed cutters 28' which'ias` in the previous example are. of. flat cross-section as shown in' Figures l5-and 16. `Each cutter is provided with anoperative cutting face which is partly straight as atlllil` and partly curved .as at 41, and at its rear end isformed.` with aitoothed sectortd; The? cutters are mounted on separate pivotl pins 3d, each of which extends half-way across the width of the respective cutter slot 2l.

The rear end of the body 25 has a large circular bore 3| in which slides a carrier membei 32, the end 33 of which is adapted to` be attached to the jack rod or drill rod. A pair of toothed racks 34 extend forwardly from the front end of the carrier member 32 and each engages with the toothed sector 29 of a cutter. These racks are adapted to slide to and fro and occupy one half of the cutter slots, and they are also adapted to occupy the space between one side of the said slots and the cutter pivot pins 30 as shown in Figure l0. A shoulder 55 having a bore 35 is provided at the forward end of theA cylindrical bore 3l. Each slot thus accommodates a cutter and a rack side by side and as the racks are moved forwardly they will lie alongside the cutters and provide abutments for taking the lateral thrust caused by the engagement of the extended cutters with 4the side of the hole. Retaining bridge members 3l are welded across the rearward ends of the slots 2l. The rack carrier member 32 is provided with a large internal .bore 33 in communication with a small bore 39 through which washing fluid may ybe supplied.- The enlarged .bore 38 accommodates a helical spring 40 which bears against the shoulder 35. The action of this spring tends to maintain the carrier member 32 in a position in which the cutters are withdrawn within their slots as indicated in Figure '7.

A stop member is mounted on the body of the tool and consists of a ring 4l formed integrally with a pair of arms 42 which pass through slots 42a in the body and engage the shoulders 34a of the` racks 34 when the blades of the cutters are in their withdrawn or closed position. The ring 4l is retained in place by means of a collar 43 secured to the rear end of the body 25. It will be understood that rotation is applied to the carrier 32 on which the racks 34 are mount-l ed and is transmitted to the body 25 through the racks which are laterally engaged in the cutter slots as previously described. In use, the tool is advanced into the hole until the centre piece 26 is engaged with the end thereof, after which further forward movement causes the carrier member 32 to be moved into the body against the action of the spring 4t and actuates the cutters 23 outwardly by means of the toothed racks 34 engaging with the toothed sectors 29. When the cutters have been fuliy extended further movementY is prevented by the abutment of the forward end of the carrier member 32 against the shoulder within the body.

The cutters are in the form of blades 44 of flat cross-section having a pivot hole 45 near one end and one side thereof, the toothed sector 29 being concentric with the said hole. The cutting edge comprises a straight portion 46 extending from near the pivot 45 -to the further end of the blade where it merges into a curved portion 41. The

edge isdrilled transversely as indicated at "48 and receives standard tapered diamond mount ings 49.

As previously mentioned, the carrier member'32 is` centrally boredl for admitting washing liquid, and there is 1a continuation bore in the body 25 through which the liquid is supplied tothe cutter slots. i. .-1 r

It will be understood that the formsof counterboring .tool described above are yespecially intended for enlarging the inner ends of shot holes to enable bigger explosive charges` to be employed inrocl:` blasting. Howeventhe invention may ob+ viously be applied to many other uses where a counterbore or internal cutting operation is required. By making provision for the employment of centre pieces of varying lengths, the counterbore may be made at any desired distance, within limits, from the end of the hole. The construction permits of the supply of liquid for washing away the cuttings resulting from the operation of the tool.

I claim:

l. A counterboring tool comprising a body adapted to be introduced into a hole, means on the body whereby it may be rotated and fed forwardly within the hole, said body having a slot, pivoted cutters located in said slot, said cutters being in overlapping relation, means ad-apted to the bodywhereby Vit may be rotated and, fed forl wardly within the hole, said body having a slot, pivoted cutters located in said slot, said cutters being in overlapping relation, means adapted to have thrust engagement with the bottom of the hole for effecting lateral movement of the `cutters into operative cutting position, and guide and abutment means on said body adapted to contact along a lower portion of the side of each cutter .to afford support against lateral thrust on the cutter when in the extending position in counterboring, each of said cutters having a toothed sector, rack means slidable within said body and meshing with said toothed sectors, said rack means lying alongside and engaging each cutter to form said abutment means.

3. A counterboring tool comprising a body adapted to be introduced into a holel means on the body whereby it may be rotated and fed forwardly within the hole, said body having a slot, pivoted cutters located in said slot, said cutters being in overlapping relation, means adapted to have thrust engagement with the bottom of the hole for effecting lateral movement of the cutters into operative cutting position, and guide and abutment means on sai-d body adapted to contact along a lower portion of the side of each cutter to afford support against lateral thrust on the cutter when in the extending position in counterboring, rack means for actuating said cutters in operative position, said rack means comprising a pair of racks arranged so that the rack for actuating one cutter extends alongside and engages the other cutter and forms said abutment means therefor.

4. A counterboring tool comprising a `body adapted to beintroduced into a hole, means on the body'whereby it may be rotated and fed forwardly Within the hole, said `body having a'slot, pivoted cutters located in 'said slot, said cutters being in overlapping relation, means adapted to .have thrust .engagement with the bottom 0f the hole for elec'timr lateral vmovement of vthe lcuttersinto operative cutting position, and `guide vand abutment means on said body adapted to contact along a lower portion of the side of each cutter to afford support against lateral thrust on the cutter when in the extending position in-oounterboring, a carrier member sldable relatively to Psaid, body, means for rotating and forwardly feeding said carrier member, rack members on said carrier member, said cutters having toothed sectors meshing with said rack members, said racks sliding within .slots in said body, whereby a rotary drive is transmitted to said body, said racks extending `alongside and engaging the cutters vto form said abutmentmeans.

` PERCY COX. 

